The proposed research investigates factors related to the execution of breathing in health and disease. Three projects are carried forward. The first entails determining the pathophysiology and associated abnormalities in periodic upper airway occlusion during sleep. The proposed research involves the use of tracheal breath sounds to detect the presence of apnea and analysis of these breath sounds in order to determine the presence of narrowing of the upper airway. In addition, the role of elevated pharyngeal resistance will be investigated. The second project is carried out on anesthetized animals and attempts to define the neural factors underlying the termination of inspiration. "Off-switch" neurons will be identified and correlated with the presence and extent of inspiratory inhibition. The third project involves study of the basic factors related to the genesis of inspiratory activity in a simple nervous system, the lamprey. Single cell recordings will be made intracellularly to determine the possible existence of pacemaker activity in neurons which project to vagal respiratory motoneurons.